Field of the Disclosure
Embodiments generally relate to input sensing and, in particular, to a technique for hybrid large dynamic range capacitance sensing.
Description of the Related Art
Input devices including proximity sensor devices (also commonly called touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, in which the proximity sensor device determines the presence, location, and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Input devices include processing circuitry that may include a charge integrator and other processing components. The charge integrator integrates a change in charge presented to an input of the charge integrator that happens as a result of driving a sensor electrode with a signal for capacitive sensing. The charge integrator has a dynamic range, which indicates the range of charge change that can be accommodated by the charge integrator. Outside of this range, the output of the charge integrator does not vary linearly with the change of charge input to the charge integrator.
The dynamic range of a charge integrator can be increased by increasing the size of a feedback capacitor of the charge integrator. However, in integrated circuits, the amount of area consumed by a capacitor is dependent on the capacitance value of the capacitor. Thus, if there is a desire to reduce the size of an integrated circuit that is used for processing sensing signals related to capacitive sensing, then a solution other than simply increasing the size of a capacitor is needed.